My solution.......

SELECT
DISTINCT Num
FROM (
SELECT
CASE WHEN Num=@prevnum THEN @count:=@count+1 ELSE @count:=1 END,
CASE WHEN @count>=3 THEN Num ELSE NULL END AS Num,
@prevnum:=Num
FROM Logs, (SELECT @prevnum:=NULL, @count:=0) AS A
) AS B
WHERE Num IS NOT NULL